In order to clarify, the flapper is synchronised with the engine. Till 4000-5000 rm the bike works with only half of power (injectors). Above that revs the power is progressively and totally available: all injectors are on and the flapper opens allowing the exit of gases. This is a way to control the torque at low revs.
If we take off the servo, we open the flapper permanentely that increase the torque at low revs (<4000 rm). Something like when we apply a aftermark exhaust. It could be nice because we feel the power and sound earlier, but in low adherence roads it could be a disaster. For instance, is not recomendable for me, cause i use my lady in all weather conditions and i no dot have a throttle control...

In order to clarify, the flapper is synchronised with the engine. Till 4000-5000 rm the bike works with only half of power (injectors).

Say whaaaaaaaaa? (the flapper is there to abate the noise, it routes the exhaust through more baffles in the muffler at low RPM so it can pass EPA noise restrictions in the U.S. for the low-speed ride-by noise test; it has nothing to do with power).

And I've never in my life heard of an engine builder associating a longer exhaust runner with increased low-RPM torque.

Actually a longer exhaust does produce a more linear power curve. But it is not substantial enough to for a high horse power bike make much of a difference. As for the exhaust valve "flap." No big deal. Leave it, get rid of it, depends on what you plan to do with the bike.

It's the other way around. A longer/larger primary decreases back pressure, so at low RPM, the combustion chamber doesn't scavenge as easily (there's not a lot of vacuum on the exhaust side due to the large pipes), and the engine is actually less efficient. At the same time, at higher RPM, the increased volume of the collector allows the engine to exhaust spent gasses more easily within its reduced cycle time, resulting in higher torque at the higher RPM, which should also result in a higher total horsepower. While you'll usually see a higher net hp number with long-tubes, it's not that usable on the street since you have to rev the engine to high hell to get there, and is the reason you generally don't put long-tubes on a street motor unless you like to drive around in first gear all the time.

It's the other way around. A longer/larger primary decreases back pressure, so at low RPM, the combustion chamber doesn't scavenge as easily (there's not a lot of vacuum on the exhaust side due to the large pipes), and the engine is actually less efficient. At the same time, at higher RPM, the increased volume of the collector allows the engine to exhaust spent gasses more easily within its reduced cycle time, resulting in higher torque at the higher RPM, which should also result in a higher total horsepower. While you'll usually see a higher net hp number with long-tubes, it's not that usable on the street since you have to rev the engine to high hell to get there, and is the reason you generally don't put long-tubes on a street motor unless you like to drive around in first gear all the time.

What you said is true for the INTAKE runners.

no. its true about the exhaust runners too.
because its NOT FUCKING GOD DAM MOTHERFUCKING BACKPRESSURE.... its resonance tuning... so the same theory applies.

This is a 5 min. mod on a '12. No need to remove seat or unbolt or drill anything. Small panel under tail has 3 plastic push screws you remove to gain access to servo. After removing panel rotate servo wheel (note where you start) clockwise to remove cable. Return servo wheel to original position. Close panel, done.

Thanks for this it really only took 5 minutes and it no longer sounds like a vesper.

It's the other way around. A longer/larger primary decreases back pressure, so at low RPM, the combustion chamber doesn't scavenge as easily (there's not a lot of vacuum on the exhaust side due to the large pipes), and the engine is actually less efficient. At the same time, at higher RPM, the increased volume of the collector allows the engine to exhaust spent gasses more easily within its reduced cycle time, resulting in higher torque at the higher RPM, which should also result in a higher total horsepower. While you'll usually see a higher net hp number with long-tubes, it's not that usable on the street since you have to rev the engine to high hell to get there, and is the reason you generally don't put long-tubes on a street motor unless you like to drive around in first gear all the time.

What you said is true for the INTAKE runners.

SMFH.......
Holy sh!t! I've been doing it wrong for the last 40 yrs. Glad I saw this, now maybe I can be even faster. SCARY.

Thanks for this it really only took 5 minutes and it no longer sounds like a vesper.

Sent from my fax

Glad to help out bro. When I did mine, before I installed my Voodoo, I didn't think it would make much of a difference. I ride with music so it didn't seem that loud. Then one day stuck behind a chick (sorry girls) on her phone I gave her a twist and she twitched and dropped her f@ckin' phone.

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